SPEAKER_1: Welcome to StarTalk, your place in the universe where science and pop culture collide.
SPEAKER_1: StarTalk begins right now.
SPEAKER_1: Welcome back to StarTalk Radio.
SPEAKER_1: I'm your host, Neil deGrasse Tyson, astrophysicist with the American Museum of Natural History in New York City.
SPEAKER_1: We're going straight into time travel questions.
SPEAKER_1: Time travel questions, I need help, because these questions come to us from the internet, from Facebook and Twitter and on the phone and Google Plus.
SPEAKER_1: And so I combed the neighborhood, and I found Colin Jost wandering.
SPEAKER_1: Colin, welcome to StarTalk Radio.
SPEAKER_2: Thank you very much, it's great to be here.
SPEAKER_1: So you've been like a comedian your whole life.
SPEAKER_1: When you were a kid, did your parents say, what are you, a comedian?
SPEAKER_1: Were you one of those?
SPEAKER_2: I totally was.
SPEAKER_2: I was in grade school, I was impersonating David Letterman and doing David Letterman shows.
SPEAKER_1: You were the class clown.
SPEAKER_2: I was, well, I wasn't like the goofy class clown.
SPEAKER_2: I was trying to, aspiring to be the smart class clown.
SPEAKER_1: The smart class clown, good, good, good.
SPEAKER_1: I wonder if anyone ever thought that it would amount to anything in your life.
SPEAKER_2: I don't know.
SPEAKER_1: Wait, wait, actually, has it?
SPEAKER_2: Yeah, well, that's a great first question.
SPEAKER_2: Enough that I'm here, I guess.
SPEAKER_1: Well, welcome, welcome.
SPEAKER_1: You come quite pedigreed.
SPEAKER_1: You're a writer for Saturday Night Live.
SPEAKER_1: I did a little bit of homework on you, excellent.
SPEAKER_1: And also, you do stand up and you can be found around town.
SPEAKER_1: And you tweet at TheColinJost.
SPEAKER_2: That's right, yeah.
SPEAKER_1: All right, we'll be following you there.
SPEAKER_1: So I brought you in to just kind of cull these questions.
SPEAKER_1: I haven't actually seen the questions yet, but you have.
SPEAKER_1: And so just fire them in.
SPEAKER_2: Fire away.
SPEAKER_1: I'm sitting in ready for you.
SPEAKER_2: This is great, they look really good to me.
SPEAKER_2: So the first one is just a pretty great question to start off time travel, which is, it's coming from Facebook, from a guy named Sean Karp on Facebook.
SPEAKER_1: Sean Karp.
SPEAKER_2: Sean Karp.
SPEAKER_2: And the question starts, what is time?
SPEAKER_2: Really nice intro.
SPEAKER_2: It continues, what is time?
SPEAKER_1: Although, so he's not satisfied with just the-
SPEAKER_2: He's not satisfied.
SPEAKER_2: This is not, you'll see there's a paragraph here, so he's not satisfied with anything.
SPEAKER_1: Okay, let's go.
SPEAKER_2: So, what is time?
SPEAKER_2: And he says, in A Sound of Thunder by Ray Bradbury, he speaks of time as a linear thing, which can be altered.
SPEAKER_2: However, in Star Trek, the 2009, he points out, Star Trek, time is also linear, but can be diverted into parallel streams like a river or a highway.
SPEAKER_2: The doctor refers to time like this.
SPEAKER_2: People assume-
SPEAKER_1: Excuse me, doctor as in Doctor Who, to show the doctor who, yeah, yeah.
SPEAKER_2: I'm assuming, unless it's just his own personal physician launching into it.
SPEAKER_1: Into the metaphysics of time.
SPEAKER_2: Tell you about time first, you know, in the middle of a proctology example.
SPEAKER_2: Let's talk about time first thing.
SPEAKER_2: The doctor refers to time like this.
SPEAKER_2: People assume that time is a strict progression of cause to effect, but actually, from a nonlinear, non-subjective viewpoint, it's more like a big ball of wibbly wobbly, timey wimey stuff.
SPEAKER_2: And he says, are any of these explanations more true?
SPEAKER_2: Are none even close?
SPEAKER_2: Other thoughts?
SPEAKER_1: Well, okay, excellent.
SPEAKER_1: And a beautiful reference there with three sources of science fiction, including the late Ray Bradbury.
SPEAKER_2: That's right.
SPEAKER_1: In fact.
SPEAKER_1: So time, all we can tell you of time is how we measure it and what consequences different phenomenon and behavior of the universe have upon it.
SPEAKER_1: So here we are sort of progressing through time, second after second, and we're prisoners of the present, forever moving between the past and the future.
SPEAKER_1: That's how we think of it.
SPEAKER_1: However, if I set you into motion, the very clearly identified and well-tested laws of relativity tell you that I can slow down or speed up your time relative to other things around you.
SPEAKER_1: So time in that sense is not linear.
SPEAKER_1: It can be stretched or shrunk.
SPEAKER_1: Or shrunk relative to other things that are around it.
SPEAKER_1: And not only that, in the vicinity of supermassive black holes that distort the fabric of space and time, because the fabric of the universe is not just what it does structurally to the space.
SPEAKER_1: It's the fabric of what the time is doing as well.
SPEAKER_1: So imagine two black holes ready to collide.
SPEAKER_1: That's an awesome disturbance in the fabric of space time.
SPEAKER_2: And so a black hole is an area where the light, the energy in it is traveling faster than the speed of light.
SPEAKER_1: Well, no.
SPEAKER_1: So once you fall into a black hole, you never come out, not even if you are a beam of light.
SPEAKER_1: So that's why it's black.
SPEAKER_1: And that's why we sensibly call it a hole.
SPEAKER_2: So if you think of a beam of light struggling to get out of a drain, it's not even getting out.
SPEAKER_1: It's not even getting out, therefore it's black.
SPEAKER_1: And so the consequence of this, it's not just simply that the light can't get out.
SPEAKER_1: Space curves back upon itself so that the light is trying to get out, but there is no pathway for it to occupy.
SPEAKER_1: And that is a severe curvature of space and time.
SPEAKER_1: And so of these three definitions here as represented in science fiction, I'd have to go with the doctor in the series Dr.
SPEAKER_1: Who.
SPEAKER_1: Dr.
SPEAKER_1: Azan.
SPEAKER_1: Right now, wiggly, wobbly, whimy.
SPEAKER_2: Yeah, wiggly, wobbly, timey, whimy stuff.
SPEAKER_1: Yeah, it's, now, about whether time can split, we simply don't know.
SPEAKER_1: Is there some other universe where you are left-handed and not right-handed that split at some point in your, I mean, we just don't know.
SPEAKER_1: We just got out, we have a hard enough time trying to understand our one universe.
SPEAKER_2: Yeah.
SPEAKER_1: Much less rivers that might flow from it.
SPEAKER_2: People have that, I think that people have that fantasy of, oh, if I had another life, I would do this.
SPEAKER_2: And if I had another life, I would do this.
SPEAKER_1: And they're hoping that that life is actually going on right now.
SPEAKER_2: Somewhere, yeah.
SPEAKER_1: In another universe.
SPEAKER_1: So I go with the Dr.
SPEAKER_1: Who on that one.
SPEAKER_2: And when we're talking about black holes, so maybe this is a more elementary question, but where does all the stuff go that's getting sucked in?
SPEAKER_1: Yeah, that's an elementary and extraordinarily good question.
SPEAKER_1: It can be both at the same time.
SPEAKER_2: Dumb and smart, right.
SPEAKER_2: In parallel worlds, I'm dumb and smart.
SPEAKER_1: So every law of physics that we know says that once you fall into a black hole, you will collapse down to what we call a singularity.
SPEAKER_1: The, by the way, that was our word first.
SPEAKER_1: Who's this guy who's been using it for-
SPEAKER_2: With cell phones, with singularity like-
SPEAKER_1: Yeah, so Ray Kurzweil has been using that.
SPEAKER_1: He stole that from us.
SPEAKER_1: Just some telling you right now.
SPEAKER_1: He's saying that's the day in the future where computers get faster and computationally than the human brain, and then you can't distinguish the two and you upload your mind into a computer and live forever.
SPEAKER_1: It's our word, singularity.
SPEAKER_1: So in the center of a black hole, all matter and energy collapse to that infinitesimal point.
SPEAKER_1: And we don't know what happens at that point.
SPEAKER_1: Physics ends at that point.
SPEAKER_1: And so we need new laws of physics, like string theory and other things, but they're working on it.
SPEAKER_1: We've got top people working on that.
SPEAKER_2: And is there a black hole that's anywhere near enough that even in centuries from now, we'll send something into it to find out or no?
SPEAKER_1: Well.
SPEAKER_2: Is that a hard thing to know?
SPEAKER_1: You want to go?
SPEAKER_2: Well, I thought we'd start like the traditional way, monkey, send a dog.
SPEAKER_1: Yeah, a tampster first.
SPEAKER_2: Yeah, exactly.
SPEAKER_1: Anyway, we got to close out this segment.
SPEAKER_1: We'll see you after the break.
SPEAKER_1: This is StarTalk Radio, and we're in the Cosmic Queries part of the show.
SPEAKER_1: I'm your host, Neil deGrasse Tyson, and I'm with Colin Jost.
SPEAKER_1: Colin, welcome to StarTalk.
SPEAKER_1: Did I pronounce your name right, Jost?
SPEAKER_2: Colin, but Jost, yeah, you're right.
SPEAKER_1: Colin Jost.
SPEAKER_2: Most people get Jost wrong, so you're already ahead of the game.
SPEAKER_1: No, I'm only half, okay, because I did better than others in that, and worse than the other, all right.
SPEAKER_1: No, that makes me dead even, I think.
SPEAKER_1: I got you on to just ask me these questions.
SPEAKER_1: You're going to be sort of the everyman person out there.
SPEAKER_1: Because we get questions, and for this particular show, we've culled together all the questions on time travel, because that's what this show has been about.
SPEAKER_1: I've not seen these questions in advance, but you've reviewed them from Facebook and Twitter and every other way people have access to us.
SPEAKER_1: So fire on.
SPEAKER_2: Yeah.
SPEAKER_2: So this next one is from Google+, like even better.
SPEAKER_1: I never met Google+.
SPEAKER_2: Even better than Google, just a little bit better.
SPEAKER_1: So Mr.
SPEAKER_1: Plus asked a question.
SPEAKER_2: A little more charged.
SPEAKER_2: This question comes from Frasier Kane of the website Universe Today, and it's a question I've also wondered many times.
SPEAKER_2: Doesn't the fact that there are no time travelers now prove that time travel will never be invented in the future?
SPEAKER_1: Yeah, that's an excellent point.
SPEAKER_1: And I've always thought about that because I said to myself, in fact, if you watch the TV, the CBS sitcom, The Big Bang Theory, in the roommate contract of, I know you got to be totally in the show for this, but in the roommate contract, it's stipulated that if I'm getting the details of it wrong, the sense of it is right.
SPEAKER_2: They'll still be very excited.
SPEAKER_1: If any one of them invents a time machine in the future, they have to go back to that moment that they're reading that phrase in the roommate contract to show up in the room.
SPEAKER_1: And so they're going through the contract and then they pause for a moment.
SPEAKER_1: Nope, okay, you're not the one who invents the time machine in the future.
SPEAKER_2: That's the ultimate, like, let's agree to meet back here 10 years from now, but it's at the same time.
SPEAKER_1: Exactly.
SPEAKER_1: And so I think that's a pretty good argument.
SPEAKER_1: And I don't have a rebuttal to that.
SPEAKER_2: But what if people are hiding it?
SPEAKER_2: What if people have come back but are not telling people for some reason because they don't want to give something away?
SPEAKER_1: There's a quote, I think it was from Raoul Dahl, but others perhaps have said it, that the only secret that can be kept between two people is when one of them is dead.
SPEAKER_1: So I'm pretty sure that if a time machine were out there, people would have figured that one out.
SPEAKER_1: It's been rumored that the reason why the Titanic sank is because in the future they invented a time machine and everyone wants to go back to the Titanic to see the iceberg when it hits and then it overloaded the Titanic and it sank.
SPEAKER_2: Well, now I'm convinced.
SPEAKER_1: So here's the evidence.
SPEAKER_1: You're looking for evidence?
SPEAKER_2: There we go.
SPEAKER_1: We got it.
SPEAKER_1: That's a pretty good one.
SPEAKER_2: Yeah.
SPEAKER_1: And it might be that your time travel machine can only take you into the future and then you don't have these paradoxes of killing your grandmother and then you're never born to go back in the-
SPEAKER_2: Yeah, we're back to the future stuff.
SPEAKER_1: Yeah, yeah, exactly.
SPEAKER_2: Because there's a movie too called Looper or Loopers with Bruce Willis and he goes back in time.
SPEAKER_2: He's like an assassin that goes back in time and he goes back and he's scheduled to kill himself so he has to like figure out what to do about it.
SPEAKER_1: You know what's interesting?
SPEAKER_1: In all these TV shows, they have people going back and killing people.
SPEAKER_1: All you have to do is pick a time where two of your ancestors who mated produced one of your ancestors and all you have to do is prevent them from mating.
SPEAKER_1: You don't have to kill anybody, just your great, great, great, great, great grandparents.
SPEAKER_1: Prevent them from meeting.
SPEAKER_1: You would have never been born.
SPEAKER_2: Just enough of the killing.
SPEAKER_1: Forget the blood and guts.
SPEAKER_1: And so it doesn't take much to completely alter the path of who's alive and who was never born and who was never conceived in this world.
SPEAKER_2: Yeah.
SPEAKER_2: All right.
SPEAKER_2: Next question here comes from Facebook, DeRay Pringle or DeRay Pringle.
SPEAKER_2: And the question is, if I had a time machine like HG.
SPEAKER_2: Wells, if I traveled back in time six months, would I not find myself floating in space with the earth on the other side of the sun?
SPEAKER_2: And if I was in LA and traveled back in time three hours, wouldn't I find myself roughly in New York and a few feet off the ground?
SPEAKER_1: So what's going on there, of course, is it presumes that the time machine is only working in the time coordinate.
SPEAKER_1: But to quote, who was it, it was not Einstein, I think it was, it'll come to me in a moment, one of the great physicists of the early 20th century upon realizing the implications of relativity noted that no one has ever been at a place without there having been a time attached to it.
SPEAKER_1: And no one has existed in time without being at a place.
SPEAKER_1: And so forever space and time, now in our new understanding of the fabric of the universe, space and time are part of the same coordinate system.
SPEAKER_1: So an intelligently rendered time machine, and this is a very clever and perceptive point of Mr.
SPEAKER_1: Pringle, a properly conceived time machine would recognize, maybe it's a setting in the settings function, it's like, put me back in time and the same place that I am relative to everything else.
SPEAKER_1: But otherwise, if you're only moving back in time, you're correct.
SPEAKER_1: You go back in time six months, you are floating in space and earth is on the other side of the sun.
SPEAKER_1: Then the side of you not facing the sun will freeze and the side of you facing your sun will burn.
SPEAKER_2: Wow.
SPEAKER_1: That's what happens when you're in space.
SPEAKER_1: Well, actually, well, you can rotate rotisserie style to stay warm, but then you'll just suffocate.
SPEAKER_1: So you got to specify location as well as time.
SPEAKER_1: Otherwise you're hosed.
SPEAKER_2: Is that when you talk about like when, not you, but when one talks about time as a dimension, is that a way to think about it too, that it's almost like on an axis and they're all one point?
SPEAKER_1: It is totally an axis.
SPEAKER_1: It's totally an axis.
SPEAKER_1: And so you want to choose the axis, the movement in time, back in time, so that the space carries you with the object that you care about, be it the planetary surface or whatever else you're doing.
SPEAKER_1: By the way, the sun is in orbit around the center of the galaxy.
SPEAKER_1: If you go back in time a million years, you want to make sure you were not only on earth, but that earth was still part of the sun and the sun's orbit around the center of the galaxy.
SPEAKER_1: Not only does earth and the moon orbit each other, earth and the sun orbit each other, and the sun and the center of the galaxy do their dance as well.
SPEAKER_1: So it's quite the ballet.
SPEAKER_2: This is a related question from Twitter from Sean Sanford.
SPEAKER_2: And this says, when time traveling, would one need to travel in exact one-year increments to show up at the same location on earth?
SPEAKER_1: Yeah.
SPEAKER_1: So if you only had the capacity to travel in time, yeah, you'd have to sort of do the one-year increment.
SPEAKER_1: But like I said, the sun in that one year has moved mightily in its orbit around the center of the galaxy.
SPEAKER_2: And other things have changed, obviously, relative to where you were.
SPEAKER_1: Exactly.
SPEAKER_1: So you have to think about that.
SPEAKER_1: I'm glad people are concerning themselves.
SPEAKER_2: It's a very high level of concern for time travel.
SPEAKER_1: It's a much deeper...
SPEAKER_2: Than like, do I get a toothbrush?
SPEAKER_2: What's the situation there?
SPEAKER_1: Exactly.
SPEAKER_2: It's very high level concerns.
SPEAKER_2: This next one is on Twitter.
SPEAKER_2: It's from Adrian Jones.
SPEAKER_2: The question is, if we could fold two points of space-time together, what would happen to the matter that was between those two points?
SPEAKER_1: Fold two points in space-time?
SPEAKER_1: Oh.
SPEAKER_1: Well, you can't because the two points in time will not correspond.
SPEAKER_1: They're two different places on the time axis.
SPEAKER_1: You can't have time t equals zero in the same place as time t equals five because they're different places on the axis.
SPEAKER_1: If you fold them, you're folding them in a higher dimension, so they're near each other.
SPEAKER_1: If you step above them in a higher dimension and look at them, they're not actually in the same place.
SPEAKER_1: Just to make that clearer, if you took a sheet of paper, and I've got one right here, even though it's radio, you can listen to it.
SPEAKER_1: I've got a sheet of paper, eight and a half by 11, and I'm curling the two edges.
SPEAKER_1: I have the two edges touching each other now.
SPEAKER_1: I can say they're in the same place, but no, they're not.
SPEAKER_2: They're not, actually.
SPEAKER_1: They're not, actually.
SPEAKER_1: Now, what I'll do is I'll punch a hole through one to get to the other, a little wormhole, and I've just warped the fabric of space, traveled through a wormhole, landed on the other side.
SPEAKER_1: Now I unfold the sheet of paper, and I just cross the sheet of paper instantly in what might have otherwise taken me some unacceptably long period of time, such as what they do in Star Trek.
SPEAKER_1: They invoke their warp drives, they take their destination, warp their location close to it, they travel through this warp in the fabric of space and time, they unfold it, and they cross the galaxy during the TV commercial.
SPEAKER_1: That's how that works.
SPEAKER_2: That sounds awesome.
SPEAKER_2: That's a great commute.
SPEAKER_1: In what would have otherwise taken across the galaxy hundreds of thousands of years, even at the speed of light.
SPEAKER_1: So it's a legitimate way to cheat the laws of relativity.
SPEAKER_2: So the detrain going uptown is like the exact opposite of that.
SPEAKER_2: It somehow manages to...
SPEAKER_1: To lengthen the time it takes to expand.
SPEAKER_2: That's awesome.
SPEAKER_1: That's a New York City reference there.
SPEAKER_2: That's a train that runs uptown in New York City.
SPEAKER_2: All right.
SPEAKER_2: Next question here is from a website.
SPEAKER_2: It's from Drew McDowell.
SPEAKER_2: I've heard Star Trek The Voyage Home used as a reference on the show before and actually had a burning question in my mind.
SPEAKER_2: They're talking about using certain velocities to use the sun's pull to time travel with.
SPEAKER_2: My question is, would there really be enough safe distance where the sun's pull could be used to gather enough speed, or would it just pull you in?
SPEAKER_1: So they're talking about Star Trek movie four.
SPEAKER_2: So it's like using what the gravity of your location with the sun to increase the velocity.
SPEAKER_1: So Colin, what we'll do is we'll get back to that after this break.
SPEAKER_2: Oh, it's a cliffhanger.
SPEAKER_2: It's a cliffhanger.
SPEAKER_1: We'll see you in a moment.
SPEAKER_1: This is StarTalk Radio.
SPEAKER_1: I'm your host, Neil deGrasse Tyson, astrophysicist.
SPEAKER_1: We're in the Cosmic Queries part of the time travel show.
SPEAKER_1: And I found him wandering the streets, Colin Jost.
SPEAKER_1: Colin, welcome to StarTalk.
SPEAKER_2: Thank you, great to be here.
SPEAKER_1: He's gonna be reading questions, submitted by all means of communication back to StarTalk.
SPEAKER_1: And by the way, Colin, if we want to find you, you're the Colin Jost.
SPEAKER_2: That's right.
SPEAKER_1: On Twitter.
SPEAKER_1: So it's like...
SPEAKER_2: And I've been enjoying all your tweets too.
SPEAKER_2: Thank you for your curiosity.
SPEAKER_2: So it's really cool.
SPEAKER_1: Thank you, thank you.
SPEAKER_2: A lot of great Mars facts that I did not know.
SPEAKER_1: So before the break, you left off with a question.
SPEAKER_1: Who is it from?
SPEAKER_2: This is a question from Drew McDowell.
SPEAKER_1: Drew McDowell.
SPEAKER_1: So he had asked about the Star Trek, The Voyage Home, Star Trek IV, which has been dubbed Save the Whales.
SPEAKER_1: That's the subtitle of that show.
SPEAKER_1: Where they go back in time to the present day of the time of the film.
SPEAKER_1: So it was 1984, I think it was, or 85.
SPEAKER_1: And so he wants to know, is there an actual speed with which you can swing by, slingshot past the sun, such as what they did in that show, in that movie, in order to go back in time?
SPEAKER_2: Right, and it says, can you use the sun's pull, but is there a safe enough distance that it wouldn't just pull you in?
SPEAKER_1: Yeah, so first of all, you cannot do what they did in the show, in the movie.
SPEAKER_2: Regardless of that.
SPEAKER_1: Regardless, right.
SPEAKER_1: So just would nip that one in the bud.
SPEAKER_2: Yes.
SPEAKER_1: Okay, so, and the only way you could do something like that is if you had vastly more powerful gravity than the sun.
SPEAKER_1: And you needed a, the fabric of space and time has to be so warped that, in fact, there's a colleague of mine who studies this.
SPEAKER_1: His name is Rich Gott.
SPEAKER_1: In fact, he's been on StarTalk before.
SPEAKER_1: He wrote a book called Time Travel in Einstein's Universe.
SPEAKER_1: And he found a solution to Einstein's equations that allows backwards time travel with the kind of a slingshot trajectory, but not around the sun.
SPEAKER_1: The sun does not disturb the fabric of space and time nearly enough to pull those up.
SPEAKER_2: What's the kindest thing that would?
SPEAKER_1: Two black holes that are in orbit around each other.
SPEAKER_1: And so you'd have to do a kind of a wiggly path around these black holes.
SPEAKER_1: And you can end up in the past of your own world line before you had left to go on that trip.
SPEAKER_2: Whoa.
SPEAKER_1: Yeah, it's a very whoa moment.
SPEAKER_1: And so Star Trek, it was more exciting to do it around the edge of the sun.
SPEAKER_1: Because visually, more visually rather than just two black things in space, which is already black.
SPEAKER_1: But in principle, but in fact, I don't know that this equation had been discovered at the time the movie was conceived.
SPEAKER_1: They surely would have tapped it.
SPEAKER_1: They've got very good writers for Star Trek.
SPEAKER_1: So yeah, and now in terms of how close you can get to the sun, the ship, unless it had deflector shields working against thermal energy, the ship would have just vaporized.
SPEAKER_1: Yeah.
SPEAKER_2: Yeah.
SPEAKER_2: And so like when you, that process you were talking about with the black holes, they have way more gravity, obviously.
SPEAKER_1: Yes, they have much more.
SPEAKER_2: What determines the gravity of an object or a, like how do you get more gravity?
SPEAKER_1: Yeah, yeah.
SPEAKER_1: You want more gravity?
SPEAKER_1: You don't weigh enough on earth?
SPEAKER_2: I know, opposite diet.
SPEAKER_1: So yeah, two ways to gain weight.
SPEAKER_1: One of them is to eat more.
SPEAKER_1: Another one is to add more mass to the earth, but keep it same size.
SPEAKER_1: So here's what happens.
SPEAKER_1: If earth's just got bigger, here's the problem.
SPEAKER_1: What makes you weigh more is how close you are to the center of gravity, the center of mass of an object.
SPEAKER_1: The closer you are to it, the more you will weigh.
SPEAKER_1: The farther away you are from it, the less you will weigh.
SPEAKER_1: Another thing that matters is what is the mass of the object you're attracted to?
SPEAKER_1: So you combine these together in an equation that Isaac Newton came up with, and you have two factors operating opposite each other.
SPEAKER_1: Okay, so watch what happens.
SPEAKER_1: If I take Earth and just make it bigger without increasing its mass.
SPEAKER_2: Your gravity is actually less.
SPEAKER_1: Gravity is gonna be less.
SPEAKER_2: And so on the moon, there's less gravity.
SPEAKER_2: Is that because the mass is smaller?
SPEAKER_1: Well, so the moon is 181st as massive as the Earth.
SPEAKER_2: Gotcha.
SPEAKER_1: 181th as massive.
SPEAKER_1: So you'd think, well, you'd only weigh 181th of what you do now.
SPEAKER_1: If you were 160 pounds, you'd think you might weigh two pounds on the moon.
SPEAKER_1: No, you weigh one sixth of what you do here.
SPEAKER_1: You weigh much more than you would otherwise weigh on the moon if you just-
SPEAKER_1: Because you're closer to the center.
SPEAKER_1: Because you're closer to the center of the moon.
SPEAKER_1: Exactly.
SPEAKER_1: So the moon has one sixth Earth's gravity, even though it is 181st the mass of the Earth.
SPEAKER_1: That's how it is.
SPEAKER_2: Problem solved.
SPEAKER_1: And so in fact, when people undergo weight loss programs, by the way, you could go to a mountaintop and you're farther away from Earth.
SPEAKER_1: That's one way to lose.
SPEAKER_2: That's the easiest way to lose weight.
SPEAKER_1: That's one way to lose weight, but you really-
SPEAKER_2: Plus getting up there, you might lose some pounds.
SPEAKER_1: Yeah, so what people usually mean is that it's a mass loss problem.
SPEAKER_1: They want to lose mass.
SPEAKER_2: Yes.
SPEAKER_1: Not just weight.
SPEAKER_1: Plus you can go on a orbit and weigh nothing.
SPEAKER_1: But you'll still be chubby if you want to start it that way.
SPEAKER_2: And it's more expensive too.
SPEAKER_1: That's way more expensive than Jenny Craig, right?
SPEAKER_2: Yeah, that's a Richard Branson diet.
SPEAKER_2: All right.
SPEAKER_2: And then, so this next question here is from Peter Baxter.
SPEAKER_2: It's from Google Plus.
SPEAKER_2: And it says, if you took one year to get to the largest black hole in the universe, then you orbited it for one year, measured by a clock on board the spaceship.
SPEAKER_2: At the closest safe orbit you could, which is kind of what we're talking about almost, then afterward it took you one year to get back to earth.
SPEAKER_2: How much time would have elapsed on earth during the three years the astronaut experienced?
SPEAKER_2: Overall, is the astronaut traveling backward in time from the perspective of earth?
SPEAKER_2: It's like an intergalactic trains traveling at two speeds.
SPEAKER_1: There you go.
SPEAKER_1: Yeah, the train going from Chicago.
SPEAKER_1: Yeah, the word problem from hell, seventh grade.
SPEAKER_1: I'll start the answer to that, but we'll have to get back to the final part of that answer after this break.
SPEAKER_1: But let me begin by saying that it depends on how fast he traveled en route to the black hole and how fast he traveled en route back.
SPEAKER_1: And so we'll address that in just a moment when we come back to StarTalk Radio.
SPEAKER_1: By the way, you can find us on the web, startalkradio.net.
SPEAKER_1: See you after the break.
SPEAKER_1: This is StarTalk Radio, where we bring the universe down to Earth.
SPEAKER_1: I'm Neil deGrasse Tyson, here with Colin Jost.
SPEAKER_1: Colin, welcome to StarTalk.
SPEAKER_2: Thank you.
SPEAKER_1: We're in the Cosmic Queries time travel show, and you're bringing questions called From the Cosmos.
SPEAKER_2: That's right.
SPEAKER_1: Right here into the studio.
SPEAKER_2: Mostly from Earth so far, but we'll see.
SPEAKER_2: So far.
SPEAKER_1: And so we left off with someone who wanted some numerical, tell me that again.
SPEAKER_2: They wanted you to fully solve a math problem.
SPEAKER_2: It was basically a year to get to a giant black hole.
SPEAKER_2: You spend a year orbiting it, and then a year back to Earth.
SPEAKER_2: So three years total.
SPEAKER_2: Are you actually traveling backward in time?
SPEAKER_2: How much time has really elapsed for the traveler?
SPEAKER_1: Okay, so.
SPEAKER_2: Or I'm sorry, how much time has elapsed on Earth?
SPEAKER_1: Fortunately, we just came out of a break.
SPEAKER_1: So I was able to actually.
SPEAKER_2: Or you fully solved this whole thing, and it was great to watch.
SPEAKER_1: Dust off my relativity equations and my.
SPEAKER_1: So here's the thing.
SPEAKER_1: A nearby black hole is in the constellation Cygnus, and it was the very first black hole ever discovered and confirmed.
SPEAKER_1: It's called Cygnus X1, and it's called X because it comes from an X-ray catalog of objects.
SPEAKER_1: And we came to learn that when a star is getting flayed by a black hole, a star that's in orbit around the black hole, that the descending material can, in its attempt to spiral down the toilet bowl, can be heated to very extreme, to extreme temperatures.
SPEAKER_1: So hot that it not only radiates red hot and white hot and blue hot, blue hot is the hottest among the temperature, among the colors that you can radiate, it actually radiates in X-rays.
SPEAKER_1: You can do the calculation and show that that's how hot the material is.
SPEAKER_1: And so the first X-ray telescopes in the 1960s and early 70s were essentially discovering black holes in our midst.
SPEAKER_2: So they picked up something and they discovered it was that mass accelerating so fast.
SPEAKER_1: An ordinary star doesn't give us X-rays of that level.
SPEAKER_1: And then you look carefully and the star is orbiting something you can't even see what's there, there's your black hole.
SPEAKER_2: Wow.
SPEAKER_2: And is it speed that's making it building heat?
SPEAKER_1: Exactly.
SPEAKER_1: So as the material spirals down, it speeds faster and faster and faster.
SPEAKER_1: And there's friction as it spirals down, friction with itself, as it tries to get into this tiny little hole.
SPEAKER_1: And that heats it up.
SPEAKER_1: It heats it up ferociously.
SPEAKER_1: And you get lots of ultraviolet light, lots of X-rays and occasionally gamma rays.
SPEAKER_2: If they could sell tickets to watch that.
SPEAKER_1: I would so do it.
SPEAKER_2: Yeah, that would be like an even better Cirque du Soleil problem.
SPEAKER_1: To watch a star get flayed by a black hole.
SPEAKER_1: That's.
SPEAKER_1: So a Cygnus X-1 is 6,000 light years away, all right?
SPEAKER_1: So a beam of light, if you watched it, you'd have to wait 6,000 years for it to get there.
SPEAKER_1: So you wanna get there in one year?
SPEAKER_2: Yeah.
SPEAKER_1: Okay.
SPEAKER_2: I would love to.
SPEAKER_1: You wanna get there in one year.
SPEAKER_1: Okay, so by your own time.
SPEAKER_1: So we get bringing the equations of relativity.
SPEAKER_1: If you must know, you're comparing two times the time you on earth would measure versus the time the person traveling.
SPEAKER_2: Experiences.
SPEAKER_1: Would experience.
SPEAKER_1: And in there, there is a factor of the square root of one minus V squared over C squared.
SPEAKER_1: And V squared is your velocity, C squared is of course the speed of light.
SPEAKER_2: Yes.
SPEAKER_1: There it is.
SPEAKER_1: It's just, did I have to say that?
SPEAKER_2: What else?
SPEAKER_2: No.
SPEAKER_2: Of course.
SPEAKER_2: I wasn't thinking cookie.
SPEAKER_1: So what happens is the faster you go, the slower time ticks for you.
SPEAKER_1: And so we're gonna slow down your time so much so that only one year passes by.
SPEAKER_1: So that's damn near the speed of light.
SPEAKER_1: The point is you're going to speed, essentially the speed of light, but not quite, but close enough so that we watching you, it'll take you 6,000 years to get there.
SPEAKER_1: You, however, your clock, your watch, your metabolism, your brain thoughts, the timer on your microwave oven, everything in your ship has slowed down as far as we can tell looking at you.
SPEAKER_1: Okay, so there it is.
SPEAKER_2: So you're experiencing, you think it's a year, but we would say it's 6,000 years from here.
SPEAKER_1: That's correct.
SPEAKER_1: I think you're taking 6,000 years and you're just moving really slow.
SPEAKER_1: That's right, so that's 6,000 years there.
SPEAKER_2: So if I'm someone who's perennially late and I'm trying to find new excuses for my employer, this might be one I might want to look into.
SPEAKER_1: Maybe, we'll find you a black hole to do this.
SPEAKER_1: 6,000 years there, then we just add the year that you're in orbit around the black hole, 6,000 years back, you would have gone into our future by 12,001 years and you would have aged only three years.
SPEAKER_1: There it is, but everyone would have forgotten about you.
SPEAKER_2: So people wouldn't even be able to say, oh, you look so good, because they'd be like.
SPEAKER_1: Anyone who would have said that would have been long decomposed in the earth.
SPEAKER_1: When we come back, our final segment here in Cosmic Queries, we will see you in a moment.
SPEAKER_1: We're back in the Cosmic Queries portion of StarTalk Radio.
SPEAKER_1: By the way, we're in the Twitterverse at StarTalk Radio.
SPEAKER_1: Like us on Facebook.
SPEAKER_1: Guess what we're called?
SPEAKER_1: We're called StarTalk Radio.
SPEAKER_1: And of course, you can get our archive of shows and read blogs and get engaged in our website, startalkradio.net.
SPEAKER_1: And as always, I've got a comedian with me here in the studio who's reading me the questions.
SPEAKER_1: Colin Jost, who's a lifetime comedian ever since you were a kid in elementary school.
SPEAKER_2: As long as I can remember, I think.
SPEAKER_1: Were teachers complaining about you or are they?
SPEAKER_2: Yeah, they were surprisingly supportive, I would say.
SPEAKER_1: Really?
SPEAKER_2: I look back, I'm like, why were they letting me do this?
SPEAKER_1: Okay, so that meant you were not a disruptive comedian.
SPEAKER_1: You were just...
SPEAKER_2: No, I somehow managed to, I guess, convince them that it was...
SPEAKER_1: That was a good thing.
SPEAKER_1: It's for your own good that I'm telling these jokes.
SPEAKER_1: Excellent, excellent.
SPEAKER_1: So we're doing Cosmic Queries.
SPEAKER_1: This is our time travel show and people wrote in.
SPEAKER_1: So what do you have?
SPEAKER_2: Here's one that I think is really interesting.
SPEAKER_1: Oh wait, by the way, we left off with this guy asking, he wants to go to the nearest black hole, take a year, hang out for a year and come back.
SPEAKER_1: And I said, he ages three years and we age 12,001.
SPEAKER_1: I was just trying to back, reverse that and say, suppose Cro-Magnon Man 12,000 years ago figured this out and they just showed up today.
SPEAKER_2: That might explain Geico.
SPEAKER_1: The Geico guys.
SPEAKER_2: You've created a scientific explanation for the Geico commercial.
SPEAKER_1: I was wondering how we would finally resolve.
SPEAKER_2: How we would get to it.
SPEAKER_1: They had already figured out time travel back then and they just showed up.
SPEAKER_1: So what else you got?
SPEAKER_2: This is a question from Facebook from Daniel Owens.
SPEAKER_2: And he writes, what would be the most surprising thing to not find if you travel 100 years into the future?
SPEAKER_2: As in they haven't figured out that yet.
SPEAKER_2: So this is more speculative, I think question on your part for you to answer.
SPEAKER_1: I'm surprised at stuff we haven't figured out today.
SPEAKER_1: I don't have to go.
SPEAKER_1: You don't need to send me 100 years into the future.
SPEAKER_1: If an alien visited us today, I'd be embarrassed.
SPEAKER_1: Look, we're still pulling energy out of the ground and we still fight each other.
SPEAKER_1: We fight wars over this oil.
SPEAKER_1: We'd be the laughing stock of intelligence pieces in the galaxies.
SPEAKER_1: And they'd say, what do you do with volcanoes?
SPEAKER_1: We run.
SPEAKER_1: What do you do with hurricanes?
SPEAKER_1: We run.
SPEAKER_1: What do you do with tornadoes?
SPEAKER_1: We run.
SPEAKER_1: Haven't you solved any?
SPEAKER_1: No, I'm embarrassed.
SPEAKER_1: This is the 21st century.
SPEAKER_1: We should be in charge of the earth and not have the earth be in charge of us.
SPEAKER_2: Imagine if they came in, the aliens came back and they just found like a Spencer's gifts and they thought that was like their leading thing instead of a museum, it would be even worse.
SPEAKER_1: Yeah, you don't know who they meet first, right?
SPEAKER_1: If they land in some nudist colony or something or whatever, you know, I always wonder if they had ever, maybe they've already landed like in Times Square, but nobody noticed because they just fit right in.
SPEAKER_2: There's so much going on there already.
SPEAKER_2: Like, uh-huh, yeah, where do you wanna go?
SPEAKER_1: Exactly, when they land in Hollywood, they just fit in, you know?
SPEAKER_1: Oh no, if they landed, I tweeted this, there was some very attractive alien in full garb.
SPEAKER_2: Oh yeah.
SPEAKER_1: But I just tweeted, I said, I met the only real alien, but no one noticed, they accidentally landed in Comic-Con.
SPEAKER_2: I know, that would be the worst place for an alien to land.
SPEAKER_1: Total worst place.
SPEAKER_2: That should be probably, at least the beginning of a movie of an alien coming to Earth.
SPEAKER_1: Exactly, exactly.
SPEAKER_2: That's a really good opening scene.
SPEAKER_1: So this question was what?
SPEAKER_2: It was kind of, what do you think in 100 years from now, you're gonna be shocked that they haven't done it?
SPEAKER_1: If we still are not in control of Earth forces that would otherwise kill us, I'd be very disappointed.
SPEAKER_1: One day I wanna tap a volcano for its energy.
SPEAKER_2: Of course, and some places I do, I mean, I remember going to Iceland and seeing some of the technology they have there.
SPEAKER_1: The geothermal energy, yeah, yeah, yeah.
SPEAKER_1: I mean, maybe we have to put beer in the volcano and then we'll learn how to tap kegs just fine.
SPEAKER_1: So to somehow tap the cyclonic energy of hurricanes, I'd be surprised if we haven't sort of figured that one out.
SPEAKER_2: Have you seen how they have, people have proposed things out in the ocean that are floating, that are circulating the water temperature so it never gets that hot and cold or?
SPEAKER_1: Oh, see, so what they're trying to do is prevent the hurricane happening in the first place.
SPEAKER_1: Well, I don't mind a hurricane if it's a source of energy for us to tap.
SPEAKER_1: So the hurricane's ready to strike the coast, then you put some device in the middle, sucks all the energy out.
SPEAKER_1: And then you power the city that the hurricane would have otherwise leveled.
SPEAKER_2: That's a pretty good, come up and so the hurricane.
SPEAKER_1: Exactly, but in fact, what's really going on there is that you're tapping solar power.
SPEAKER_1: The sun is what's driving the hurricane.
SPEAKER_1: So in fact, there's a lot of wasted solar energy.
SPEAKER_1: First, that's just hitting rooftops that don't have solar panels, but also solar energy that is otherwise creating things that would destroy us.
SPEAKER_1: And also just earthquakes, the amount of energy in an earthquake.
SPEAKER_1: So I wanna be in command of Earth's forces 100 years from now.
SPEAKER_1: And I'd be disappointed if we weren't.
SPEAKER_2: Grant, that's a really good goal.
SPEAKER_1: We're running out of time, oh my gosh.
SPEAKER_2: My last thing, I was curious because it's all over the place now is with the Higgs-Boson particle, how does that affect time travel?
SPEAKER_2: Are there any thoughts about how that can either explain or help?
SPEAKER_1: Yeah, it's not obvious that it could affect time travel, but if I can get really science fiction on you.
SPEAKER_2: Yeah, please.
SPEAKER_1: Right?
SPEAKER_1: The Higgs-Boson controls the mass of particles.
SPEAKER_1: Imagine you go into a Higgs-Boson spa and it changes your mass just by walking in and walking back out.
SPEAKER_2: Well.
SPEAKER_1: That would be total command of particle physics.
SPEAKER_1: That would be an awesome weight loss program.
SPEAKER_2: Yeah, I'm sure that would be the first thing someone uses it for is to commercialize.
SPEAKER_2: Want to look 10 pounds thinner?
SPEAKER_1: Not to advance our understanding of the universe, but to take that off your belly and butt.
SPEAKER_1: Anyhow, we got to call it a day.
SPEAKER_1: Thanks Colin for being on StarTalk Radio.
SPEAKER_2: It's a pleasure, thank you for having me.
SPEAKER_1: You've been listening to StarTalk Radio.
SPEAKER_1: I'm Neil deGrasse Tyson, signing off as always, bidding you to keep looking up.